As a child, he had read the stories of a lost expedition and the ?jungle hell? which had swallowed up the white man. Even decades after it had happened, the newspapers were full of sightings and testimonies, of how the explorer had followed his ?crazy? dream of a hidden Atlantis into the heart of the Amazon - and simply disappeared.

?It?s a white man?s obsession,? admits Benedict Allen, sitting in his west London home. Allen, 39, has been a full-time film-maker and explorer since graduating from university, and is the author of seven books about his journeys. He is best known for his unique style of video diaries, recorded as he walks through places such as the harsh Namibian Desert or across Mongolia, often struggling to control pack animals and fighting the effects of solitude. This style of ?exploration? has won him both critics and admirers, but it seems to be a success, as he is developing several new series (his latest, to be shown next year, is on medicine men).

When I meet him, it is a few days before the airing of his latest TV offering, ?Colonel Fawcett?s Bones?, which outlines what might have happened to the explorer Colonel Percy Harrison Fawcett, who disappeared in the Amazon jungle over 70 years ago.

The Fawcett saga was one of those stories which helped shape Allen?s future life as an explorer and film-maker - a tale of daring (some say crazy) exploration which has since passed into myth. Allen ventured into the heart of Brazil?s Mato Grosso and the Xingu Indian reserve, to try and find the truth about Fawcett?s fabled expedition. ?I came across him as a boy, reading about all these exciting foreign places,? says Allen, ?and there he was, in every book on the Amazon. I thought ?why do people still talk about him over 70 years since he died?? What is it about this person that still attracts people??

?Historically, he is pretty well irrelevant,? he adds. ?He?s famous not for discovering something, but for becoming lost.? He laughs ironically. ?What makes him interesting, though, is that he?s like the Livingstone of the Amazon; the Amazon?s a mystery in itself, and he?s become kind of swallowed up in it in a way.?

The 58-year-old Fawcett had travelled deep into the Mato Grosso - virgin rainforest -?in April 1925, in search of a lost city which he had found described in an 18th century explorer?s manuscript. His expedition ended in tragedy, however, when he disappeared three months into his journey. No-one knows his exact fate or that of his young son, Jack, or their travelling companion Raleigh Rimmel. They had bid farewell to their Indian guides and pack animals several weeks before, opting to slog it through the jungle and hunt on the move, rather than travel by river as the local Indians chose to do. The men may have been slowly starving to death and it is known that Rimmel was limping badly, thanks to infected tick bites on his leg. However, in his last known letter, handed to their Indian guides, Fawcett wrote to this wife ?You need have no fear of any failure.? Then there was nothing.

Rumours had it that they were eaten by jaguars, or attacked by wild pigs or other animals. Others that Fawcett had actually found his hidden city and lives on there today (he was known to have strong ?mystic? beliefs). A rescue expedition sent two years later was itself surrounded by Indians and had to flee. Commander Dyott, its leader, reported shortly afterwards that: ?The Fawcett expedition [must have] perished at the hands of hostile Indians during July 1925.?

However, in 1951 a shocking twist to the tale took place. Orlando Villas Boas, one of the three famous Boas brothers who had championed Indian rights and helped establish the Xingu reserve, said that one tribe of Indians - the Kalapalo -?had confessed to the murder of Fawcett and his companions. Apparently, they had confided in him - as the only white man they trusted - that Fawcett had set up camp far away from their village; had then caused offence by shooting but not sharing a duck (the Indians being very communally minded); and compounded his error by slapping a child who had touched his machete.

Villas Boas said the Kalapalo told him that they had clubbed the white man and his companions to death, by a nearby ?Green Lagoon?. Fawcett?s body was buried there, whilst Jack and Raleigh were left for the alligators. It was a shocking admission by any account, as it could lead to severe reprisals. But there was no doubting Villas Boas? credentials. Furthermore he had proof. In exchange for ?six pounds of coloured beads and some fishing lines? the Indians led him to the lagoon, he said, where they disinterred and handed over a set of bones.

?And there it should have ended,? says Allen. Except that Fawcett?s one surviving son, Brian, disputed that the bones could be his father?s. He claimed they belonged to a shorter man, and that a set of Fawcett?s spare dentures didn?t fit the skull. Cross-examining the Kalapalos, he said: ?I found everything completely unconvincing and the story was full of contradictions.?

Thirteen expeditions in all followed Fawcett?s path into the Mato Grosso, even as the area shrank under the assault of loggers, farmers and mineral hunters. All ended in failure. The last was in 1996, when a dozen members of the team were kidnapped by the Kalapalo. Watching Allen?s tapes, you can quite clearly see that he too was nervous about meeting the Indians for the first time.

?I wanted to give their side of the story,? explains Allen. ?These people are threatened by farmers, who burn the land; the area is being eroded all the time; there?s hunters and fishers, even eco-pirates (people hunting for miracle drugs for western science) - so the Indians are understandably nervous about the white man. And they also have this extra stigma of killing Fawcett. They feel they?re carrying this burden.?

When he was met by the chief of the Kalapalo himself, Allen realised ?they were looking forward to this chance, to give their side of the story.? He hadn?t thought that they would even remember their fateful encounter 70 years before. But it soon became clear they had an enormous amount to say.

After several days (during which time Allen - ?this crazy white man? - had canoed down the river) they gathered all the menfolk together to discuss the situation, as is common for any major decision. The society was still very similar to how it would have been in Fawcett?s day (except for the odd radio or bicycle).

Allen retrieved his old photos of the explorer ?but they needed no reminding whatsoever. They knew the chief who was around at that time, they didn?t have to think back. Of course, they?re illiterate, but they have an oral history and you could see how important and carefully maintained this history was. Even as I was sitting down, you could see how the children were incorporated and beginning to learn the official version of events that are handed down.?

They told him that Fawcett had indeed made camp near to the village, but that he had continued on his journey the next day, even though the Indians warned him to turn back. They claim he had shown them one of his distress flares and that five days after he left them, they spotted smoke in the jungle (perhaps from one of the flares). ?They followed the trail, found where he had camped - then nothing, the forest was undisturbed. And that?s all they said they knew about Fawcett. They wouldn?t speculate further.?

He muses for a second. ?The inference is that they were killed by other Indians. At the time there was a group called the Iaruna, who had a raiding party sweeping through the area.?

The Kalapalo chief, Vajuvi, took Allen to the Green Lagoon, where he claimed that the bones they dug up belonged to his grandfather. He said that Villas Boas had come to them in 1951 and asked them to dig up the bones of the tallest Indian, which could then be disguised as Fawcett?s remains. Vajuvi claims that his father was away at the time, and when he returned, never forgave what had happened.

Villas Boas, now in his eighties, contradicts the Kalapalos? claims, saying they are ?pure invention on the Indian?s part?. He says that when Fawcett entered the area, he identified himself as ?Mi, ingles? (?Me, English?) and that the Indians adapted this to ?Miguelese?. When he met them in the 1950s, they told Villas Boas they had killed a ?Miguelese? in the past.

Why, Allen wonders? Why would they accuse a man who was their closest friend - Villas Boas - and one of their greatest champions, of lying? ?The Indians today are afraid there might be repercussions in relation to all this,? replies Villas Boas. Allen is torn between the two stories, saying they both ring true to a certain extent.

?I had gone in there, expecting as a film-maker to use Colonel Fawcett as a symbol of the white man intruding, and it was poor old Orlando becoming the symbol of the white intruder. In a way, I felt he was carrying the burden of all that we had done. That to me was the underlying scenario.?

However, so strong were the Kalapalos? feelings, that they refused to let Allen wander off into the jungle in the same direction that Fawcett had taken in 1925. ?Even seven decades on, it is highly relevant and lives on for these Indians,? he says.

So what was Fawcett?s contribution to history? ?Well, probably towards the end, he was being laughed at more and more by the Establishment. Maybe he was hoping to give the world something. Maybe he just couldn?t take failure. Perhaps he just pushed himself too far.? He pauses for a moment. ?He was obsessed, a hard man, not someone I can feel very sympathetic with really. I admire him for his dream, for pushing it through - but that?s as far as it goes.?